Diet and segregation of desert bighorn sheep (Ovis canadensis mexicana Merriam 1901) in Sonora, Mexico

Although bighorn sheep (Ovis canadensis mexicana) is important ecologically and economically, this species included in the NOM-059-SEMARNAT-2010, in the category of special protection. This species has adapted to arid climates, developing reproductive strategies such as segregation, which starts once the breeding season ends; in this, males and females conduct its activities in different areas. The understanding of this behavior considering bighorn sheep food preferences, will help to estimate carrying capacity of males and females in a given site. This study was conducted in the Management Unit for the Conservation of Wildlife Rancho Noche Buena , Hermosillo , Sonora during August 2014 -August -2015. The objectives were to determine diet composition of bighorn sheep and to estimate the differences between the diet of males and females during segregation. For this purpose, bighorn sheep fecal samples were collected by season, period (reproductive and segregation) and sex. Individuals were located with binoculars and observed until defecation. We used the microhistological technique and a cell catalog of the plants found in the study area to identify the plant species in fecal samples. Fifty slides of composed samples were prepared, analyzed and the plants species were classified by biological form, family and species. The relative frequency, diversity index of Shannon-Wiever and the similarity index of Kulczynski per season, sex and period were determined. Bighorn sheep diet consisted of 48 species being the herbaceous (28.8 %) and shrubs (21.3 %) the most common. Herbaceous dominated in all seasons (spring 28.4 %; summer 24.1% and fall 29.1 %), except winter (grasses 34.5 %). The diet of males during the segregation period was composed mainly of grasses (37.6 %) and the diet of females of herbaceous (31.7 %) plants. No differences in the diversity of the diet of males and females in the segregation period (H '= 1) were found and their diet were similar (80 %). However, the composition of the diet of segregated and non-segregated males had the lowest percentage of similarity (67%). The results of this study, as in other studies conducted on bighorn sheep in the state of Sonora, México showed that sexual segregation exhibited by this species in Rancho Noche Buena, was not due to food preferences and possibly, some other causes induced this behavior.Thesis. M. Sc. in Innovation in Natural Resources Management, Colegio de Postgraduados, Campus San Luis Potosí, 201